1. FIELD OF THE INVENTION
This invention relates, generally, to epoxy resins, and, specifically, to fluoroepoxy resins with high glass transition temperature for use in computer composite circuit boards and to a method of making a fluoroepoxy resin with high glass transition temperature.
2. DESCRIPTION OF THE PRIOR ART
Epoxy resins, on account of their superior strength, stability and low surface energy are important today as coatings and adhesives. Difficulties in the manufacture and use of these compounds, especially the highly fluorinated epoxy resins, are caused by the curing agents. The curing agents used in synthesizing high glass transition temperature (T.sub.g) epoxy resins are usually dianhydrides, e.g. pyromellitic dianhydride and amines, e.g. dimethylaminoethane. The defects associated with dianhydride curing agents are high melting point, e.g., the melting point of pyromellitic dianhydride is 286.degree. C., very unagressive reaction behavior with these epoxies, and a reduction of the fluorine content of the resin in comparison with the fluorinated epoxy monomer.
While the amine curing agents react more readily, these compounds are not better in regards to the high melting point and reduction of the fluorine content of the resin. These compounds are also objectionable due to the lower thermal stability and coloring of the resulting resins. Fluorinated amines give some improvement. However, these curing agents have several disadvantages which include poor long-term chemical stability, unagressive reaction behavior with respect to epoxies and excessive cost factors.
U.S. Pat. No. 4,045,408 relates to a fluorinated anhydride curing agent for fluoroepoxy resins. Polymethyl benzene is reacted with perfluoroacetone. The fluoro-substituted polymethyl benzene reaction product is oxidized to the acid. The acid is heated to form the anhydride curing agent. Gel times are in hours.
U.S. Pat. No. 4,744,783 describes inductive devices formed by making a circuit pattern on a flexible dielectric substrate and then rolling the patterned substrate into one or more coils such that the current is traveling in the same direction. The device is attached to a printed wiring board. One material suggested for the substrate of the inductive device, but not the printed wiring board, is a fluoropolymeric film. No specific substance is specified. No properties or advantages of using a fluoropolymer are noted.
The drive for high computational speeds has pushed the size of integrated circuits to smaller and smaller dimensions. Lower dielectric constant laminating resins have become necessary to preserve electronic performance. Fluoroepoxy resins inherently have low dielectric constants. However, current resin systems cannot produce material with glass transition temperatures to withstand processing and operating temperatures.